[U-Boot] [PATCH v4 4/7] env: add check/apply logic to himport_r()

[Marek Vasut]

Dear Gerlando Falauto,

> Change hashtable so that a callback function will decide whether a
> variable can be overwritten, and possibly apply the changes.
> 
> So add a new field to struct hsearch_data:
> 
>  o "apply" callback function to check whether a variable can be
>     overwritten, and possibly immediately apply the changes;
>     when NULL, no check is performed.
> 
> And a new argument to himport_r():
>  o "do_apply": whether to call the apply callback function
> 
> NOTE: This patch does not change the current behavior.

Reviewed-by: Marek Vasut <marex at denx.de>

> Signed-off-by: Gerlando Falauto <gerlando.falauto at keymile.com>
> ---
>  common/cmd_nvedit.c   |    3 ++-
>  common/env_common.c   |    8 +++++---
>  include/environment.h |    9 +++++++++
>  include/search.h      |   14 +++++++++++++-
>  lib/hashtable.c       |   20 +++++++++++++++++++-
>  5 files changed, 48 insertions(+), 6 deletions(-)
> 
> diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
> index 493aecc..983e747 100644
> --- a/common/cmd_nvedit.c
> +++ b/common/cmd_nvedit.c
> @@ -202,6 +202,7 @@ static int do_env_grep(cmd_tbl_t *cmdtp, int flag,
>   * environment variable, then (if successful) apply the changes to
> internals so * to make them effective.  Code for this function was taken
> out of * _do_env_set(), which now calls it instead.
> + * Also called as a callback function by himport_r().
>   * Returns 0 in case of success, 1 in case of failure.
>   * When (flag & H_FORCE) is set, do not print out any error message and
> force * overwriting of write-once variables.
> @@ -915,7 +916,7 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
>  	}
> 
>  	if (himport_r(&env_htab, addr, size, sep, del ? 0 : H_NOCLEAR,
> -			0, NULL) == 0) {
> +			0, NULL, 0 /* do_apply */) == 0) {
>  		error("Environment import failed: errno = %d\n", errno);
>  		return 1;
>  	}
> diff --git a/common/env_common.c b/common/env_common.c
> index 8f142ed..c6e7c4c 100644
> --- a/common/env_common.c
> +++ b/common/env_common.c
> @@ -133,7 +133,9 @@ const uchar default_environment[] = {
>  	"\0"
>  };
> 
> -struct hsearch_data env_htab;
> +struct hsearch_data env_htab = {
> +	.apply = env_check_apply,
> +};
> 
>  static uchar __env_get_char_spec(int index)
>  {
> @@ -194,7 +196,7 @@ void set_default_env(const char *s)
> 
>  	if (himport_r(&env_htab, (char *)default_environment,
>  			sizeof(default_environment), '\0', 0,
> -			0, NULL) == 0)
> +			0, NULL, 0 /* do_apply */) == 0)
>  		error("Environment import failed: errno = %d\n", errno);
> 
>  	gd->flags |= GD_FLG_ENV_READY;
> @@ -220,7 +222,7 @@ int env_import(const char *buf, int check)
>  	}
> 
>  	if (himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0', 0,
> -			0, NULL)) {
> +			0, NULL, 0 /* do_apply */)) {
>  		gd->flags |= GD_FLG_ENV_READY;
>  		return 1;
>  	}
> diff --git a/include/environment.h b/include/environment.h
> index ae3f7b6..90fb130 100644
> --- a/include/environment.h
> +++ b/include/environment.h
> @@ -184,6 +184,15 @@ void set_default_env(const char *s);
>  /* Import from binary representation into hash table */
>  int env_import(const char *buf, int check);
> 
> +/*
> + * Check if variable "name" can be changed from oldval to newval,
> + * and if so, apply the changes (e.g. baudrate).
> + * When (flag & H_FORCE) is set, it does not print out any error
> + * message and forces overwriting of write-once variables.
> + */
> +int env_check_apply(const char *name, const char *oldval,
> +			const char *newval, int flag);
> +
>  #endif /* DO_DEPS_ONLY */
> 
>  #endif /* _ENVIRONMENT_H_ */
> diff --git a/include/search.h b/include/search.h
> index 94d75fc..721c8ac 100644
> --- a/include/search.h
> +++ b/include/search.h
> @@ -57,6 +57,16 @@ struct hsearch_data {
>  	struct _ENTRY *table;
>  	unsigned int size;
>  	unsigned int filled;
> +/*
> + * Callback function which will check whether the given change for
> variable + * "name" from "oldval" to "newval" may be applied or not, and
> possibly apply + * such change.
> + * When (flag & H_FORCE) is set, it shall not print out any error message
> and + * shall force overwriting of write-once variables.
> +.* Must return 0 for approval, 1 for denial.
> + */
> +	int (*apply)(const char *name, const char *oldval,
> +			const char *newval, int flag);
>  };
> 
>  /* Create a new hashing table which will at most contain NEL elements.  */
> @@ -97,10 +107,12 @@ extern ssize_t hexport_r(struct hsearch_data *__htab,
>  /*
>   * nvars: length of vars array
>   * vars: array of strings (variable names) to import (nvars == 0 means
> all) + * do_apply: whether to call callback function to check the new
> argument, + * and possibly apply changes (false means accept everything)
>   */
>  extern int himport_r(struct hsearch_data *__htab,
>  		     const char *__env, size_t __size, const char __sep,
> -		     int __flag, int nvars, char * const vars[]);
> +		     int __flag, int nvars, char * const vars[], int do_apply);
> 
>  /* Flags for himport_r() */
>  #define	H_NOCLEAR	(1 << 0) /* do not clear hash table before 
importing */
> diff --git a/lib/hashtable.c b/lib/hashtable.c
> index 0610e86..6cfba56 100644
> --- a/lib/hashtable.c
> +++ b/lib/hashtable.c
> @@ -658,7 +658,7 @@ static int is_var_in_set(const char *name, int nvars,
> char * const vars[])
> 
>  int himport_r(struct hsearch_data *htab,
>  		const char *env, size_t size, const char sep, int flag,
> -		int nvars, char * const vars[])
> +		int nvars, char * const vars[], int do_apply)
>  {
>  	char *data, *sp, *dp, *name, *value;
> 
> @@ -772,6 +772,24 @@ int himport_r(struct hsearch_data *htab,
>  		e.key = name;
>  		e.data = value;
> 
> +		/* if there is an apply function, check what it has to say */
> +		if (do_apply && htab->apply != NULL) {
> +			debug("searching before calling cb function"
> +				" for  %s\n", name);
> +			/*
> +			 * Search for variable in existing env, so to pass
> +			 * its previous value to the apply callback
> +			 */
> +			hsearch_r(e, FIND, &rv, htab);
> +			debug("previous value was %s\n", rv ? rv->data : "");
> +			if (htab->apply(name, rv ? rv->data : NULL,
> +				value, flag)) {
> +				debug("callback function refused to set"
> +					" variable %s, skipping it!\n", name);
> +				continue;
> +			}
> +		}
> +
>  		hsearch_r(e, ENTER, &rv, htab);
>  		if (rv == NULL) {
>  			printf("himport_r: can't insert \"%s=%s\" into hash 
table\n",